Dishwasher and method of operation

ABSTRACT

A dishwasher includes an interior tub and a wash pump for pumping wash liquid to wash dishes located in the interior tub. A pump motor for driving the wash pump is regulated by a control unit that adjusts a spraying pressure of wash liquid. The method for operating a dishwasher includes sensing the degree to which wash liquid is soiled and regulating the speed of a pump motor for spraying wash liquid against the dishes, depending upon the degree to which the wash liquid is soiled. The regulation of the pump motor adjusts the wash liquid spraying pressure.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a method and apparatus for washing dishes and in particular, to an automatic dishwasher and a method for operating the same, wherein a liquid spraying pressure is adjusted according to the degree to which the dishes are soiled, thus optimizing energy efficiency while preventing damage to the dishes.

[0003] 2. Description of the Related Art

[0004] Automatic dishwashers have been widely used throughout the world in many homes and commercial establishments, e.g., restaurants. A known dishwasher is described with reference to FIG. 1. The known dishwasher includes an interior tub 1. Wash liquid filled in the interior tub 1 is drawn by a wash pump 5 and is supplied to lower and upper wash arms 9 and 10 through flow paths 6 and 7. Wash liquid supplied to the lower and upper wash arms 9 and 10 is sprayed, through nozzles 14 formed therein, onto dishes supported on lower and upper dish racks 11 and 12 to remove food substances therefrom. Wash liquid including the food substances removed from the dishes flows toward a bottom of the interior tub 1 to be collected in a sump 2. The wash liquid collected in the sump 2 passes through a filter 3 to remove solid particulate. Then, the filtered wash liquid is drawn again through a flow path 4 by the wash pump 5 to be recirculated over the dishes. After the dishwashing operation is completed, wash liquid is collected in the sump 2 and is discharged out of the tub 1, along with the separated substances (i.e., soiled materials), through a drain pump 13.

[0005] However, the known dishwasher as discussed has various drawbacks. Specifically, a pump motor for driving the wash pump 5 is operated at a constant speed in revolutions per minute (rpms) such that the wash pump 5 sprays wash liquid through nozzles 14 at a constant spraying pressure, regardless of the degree to which the dishes are soiled.

[0006] Consequently, even when washing lightly soiled dishes, the identical dishwashing operation designed to wash highly soiled dishes is performed, resulting in a waste of wash liquid and energy. Moreover, with the aforementioned dishwasher, damage may be done to dishes that are expensive or dishes having low impact resistance, such as crystal, for example.

SUMMARY OF THE INVENTION

[0007] Accordingly, the present invention has been made in an effort to solve the problems occurring in the related art, and an object of the present invention is to provide a dishwasher and a method for operating the same, wherein a wash liquid spraying pressure can be adjusted depending upon the degree to which the dishes are soiled, to avoid unnecessary consumption of wash liquid and energy. Furthermore, a wash liquid spraying pressure can be adjusted as desired by a user, to protect dishes having inferior impact resistance.

[0008] In order to achieve the above objects, according to one aspect of the present invention, a dishwasher is provided that includes an interior tub in which dishes to be washed are located; a wash pump for pumping wash liquid for washing the dishes located in the interior tub; a pump motor for driving the wash pump; a spraying mechanism for spraying wash liquid onto the dishes; and a control unit for regulating a speed of the pump motor thereby to adjust a spraying pressure of wash liquid sprayed from the spraying mechanism.

[0009] According to another aspect of the present invention, a method for operating a dishwasher includes sensing the degree to which the wash liquid is soiled upon washing dishes located in the dishwasher; regulating a speed of a pump motor for spraying wash liquid onto the dishes, depending upon the degree to which the wash liquid is soiled as sensed; and adjusting a wash liquid spraying pressure by regulating the speed of the pump motor.

[0010] The method may further include determining the degree of soil concentration in the wash liquid and calculating a rate of concentration change of the wash liquid. Additionally, a next dishwashing procedure may be implemented when the sensed soil concentration is constant and the calculated rate of concentration change is lower than a previous value.

[0011] The speed of the pump motor is regulated such that a first level of power inputted to the pump motor, when a sensed soil concentration is higher than a reference value, is greater than a second level of power inputted to the pump motor, when sensed soil concentration is lower than a reference value. Also, an instruction may be received from an operator to adjust the wash liquid spraying pressure, such that the speed of the pump motor is regulated in response to the instruction for adjusting the wash liquid spraying pressure.

[0012] According to yet another aspect of the present invention, a dishwasher is provided that includes an interior tub in which dishes to be washed are located, a wash pump for pumping wash liquid for washing the dishes located in the interior tub, a pump motor for driving the wash pump, a spraying mechanism for spraying wash liquid onto the dishes; and a control unit for regulating the speed of the pump motor to adjust a spraying pressure of wash liquid sprayed from the spraying mechanism.

[0013] The control unit regulates the speed of the pump motor by controlling a phase of power inputted to the pump motor. A sensor is also included for sensing the degree to which the wash liquid is soiled, upon washing the dishes. Specifically, the sensor senses a soil concentration in the wash liquid and calculates a rate of concentration change of the wash liquid. When the sensed soil concentration in the wash liquid is constant and the calculated rate of concentration change is lower than a previous value, the control unit implements a next dishwashing procedure.

[0014] The control unit includes a microcomputer for generating and outputting a trigger signal to control the supply of power from a power source to the pump motor; and a phase controlling driver circuit for controlling a phase of power to be supplied from the power source to the pump motor in response to the trigger signal generated and outputted by the microcomputer. As a result, the phase controlling driver circuit applies a resulting power to the pump motor.

[0015] The microcomputer controls the phase controlling driver circuit so that a first speed of the pump motor, when a sensed soil concentration is higher than a reference value, is greater than a second speed of the pump motor when a sensed soil concentration is lower than the reference value. Specifically, the higher speed of the pump motor in turn creates a higher wash liquid spraying pressure than does a lower pump motor speed.

[0016] Optionally, an operator may control the wash liquid spraying pressure by actuating a spraying pressure adjustment control.

BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The above objects, and other features and advantages of the present invention will be made apparent from the following detailed description of the preferred embodiments, given as non-limiting examples, with reference to the accompanying drawings, in which:

[0018]FIG. 1 is an exemplary front view of a prior art dishwasher;

[0019]FIG. 2 is an exemplary block diagram illustrating a dishwasher schematic, according to an aspect of the present invention;

[0020]FIGS. 3a, 3 b and 3 c are exemplary graphs illustrating waveforms of power inputted to a pump motor during operation of the dishwasher, according to an aspect of the present invention; and

[0021]FIG. 4 is an exemplary flow chart depicting a method for operating the dishwasher according to an aspect of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] The particulars shown herein are by way of example and for purposes of illustrative discussion of the embodiments of the present invention only and are presented in the cause of providing what is believed to be the most useful and readily understood description of the principles and conceptual aspects of the present invention. In this regard, no attempt is made to show structural details of the present invention in more detail than is necessary for the fundamental understanding of the present invention, and the description is taken with the drawings making apparent to those skilled in the art how the forms of the present invention may be embodied in practice.

[0023] Reference will now be made in greater detail to a preferred embodiment of the invention, an example of which is illustrated in the accompanying drawings. Wherever possible, the same reference numerals will be used throughout the drawings and the description to refer to the same or like parts.

[0024]FIG. 2 is an exemplary block diagram depicting a relevant portion of a dishwasher (the non-illustrated portions being conventional and substantially depicted in FIG. 1), according to an aspect of the present invention. The dishwasher includes a pump motor 30 and a control unit 20. The pump motor 30 drives a wash pump (not shown) that pumps wash liquid through a spraying mechanism (not shown) for spraying wash liquid onto dishes located in an interior tub (not shown). The control unit 20 functions to adjust the spraying pressure of the washing liquid by regulating the speed (i.e., revolutions per minute or rpms) of the pump motor 30.

[0025] The control unit 20 includes a microcomputer 22 and a phase controlling driver circuit 21. The microcomputer 22 generates and outputs a trigger signal for controlling a supply of power from a power source 35 to the pump motor 30. The phase controlling driver circuit 21 controls a phase of power supplied from the power source 35 to the pump motor 30 in response to the trigger signal generated and outputted by the microcomputer 22, and applies the resulting power to the pump motor 30.

[0026] That is, the microcomputer 22 calculates an optimal speed of the pump motor 30, and generates and outputs a trigger signal corresponding to the calculated optimal speed of the pump motor 30. Then, in response to the trigger signal, the phase controlling driver circuit 21 controls the phase of power supplied from the power source 35 to the pump motor 30. That is, a phase of power supplied from the power source 35 to the pump motor 30 is controlled in response to the trigger signal outputted from the microcomputer 22. As a result, the speed of the pump motor 30 is optimally regulated.

[0027]FIGS. 3a, 3 b and 3 c are exemplary graphs illustrating waveforms of power outputted from the power source 35 and inputted to the pump motor 30 in response to the trigger signals generated and outputted by the microcomputer 22.

[0028] Specifically, power is supplied to the pump motor 30 for an interval which extends from a position of a trigger signal generated and outputted by the microcomputer 22 to a zero-crossing point where a phase of power from the power source 35 is inverted, and power supply is cut off for another interval which extends from the zero-crossing point to a position of a next trigger signal. Consequently, by controlling a position of the trigger signal, power supplied to the pump motor 30 is changed, thereby regulating the speed of the pump motor 30 and adjusting the liquid spraying pressure.

[0029] The hatched portions of FIGS. 3a, 3 b and 3 c represent amounts of power supplied to the pump motor 30 in response to trigger signals. In FIGS. 3a through 3 c, the dashed lines illustrate waveforms of power outputted from the power source 35, and the solid lines illustrate waveforms of trigger signals outputted from the microcomputer 22. As can be readily seen from FIGS. 3a, 3 b and 3 c, an interval, through which power is supplied to the pump motor 30, extends from a position of a trigger signal to a next zero-crossing point. That is, power supply to the pump motor 30 has no relationship to a width of a trigger signal, and is determined by a position where a trigger signal is initially splashed.

[0030]FIGS. 3a, 3 b and 3 c illustrate waveforms in instances where the wash liquid is sprayed at a high pressure, an intermediate pressure and a low pressure, respectively. In FIG. 3a, since an entire amount of power is inputted to the pump motor 30, the pump motor 30 is rotated at high rpms. In FIGS. 3b and 3 c, as only portions of power are inputted to the pump motor 30, slip of the pump motor 30 is increased, and thus, the pump motor 30 is rotated at low rpms.

[0031] The dishwasher according to the present invention further includes a soil degree sensor 25 for sensing the degree to which the wash liquid is soiled. The soil degree sensor 25 senses the degree of soil concentration in the wash liquid and calculates a rate of concentration change of the wash liquid. Then, the soil degree sensor 25 outputs the sensed soil concentration and the calculated rate of concentration change to the microcomputer 22.

[0032] The microcomputer 22 outputs a control signal to the phase controlling driver circuit 21, to adjust the wash liquid spraying pressure depending upon the degree of soil concentration and the rate of concentration change sensed and calculated by the soil degree sensor 25. As a result, the amount of power supplied from the power source 35 to the pump motor 30 is regulated and the wash liquid spraying pressure is adjusted.

[0033] The dishwasher further includes a spraying pressure adjustment control 24 for allowing the wash liquid spraying pressure to be manually adjusted as desired by an operator. As the operator manipulates the spraying pressure adjustment control 24, an instruction for adjusting the wash liquid spraying pressure, as indicated by the operator, is inputted to the microcomputer 22. Accordingly, the microcomputer 22 transmits a control signal to the phase controlling driver circuit 21 to regulate the speed of the pump motor 30 in response to the inputted instruction.

[0034] The control unit 20 of the dishwasher controls other programmed tasks which are required for washing dishes in the dishwasher, e.g., actuation of wash and drain pumps, refilling of fresh wash liquid, operating a heater, etc. The control unit 20 is configured to implement a dishwashing procedure based on signals sensed by a variety of sensors, including a level sensor or a pressure sensor for sensing an amount of wash liquid filled in the tub and a temperature sensor for preventing the dishwasher from being overheated, for example.

[0035] Moreover, the control unit 20 further includes an interrupter 23. The interrupter 23 is connected with the microcomputer 22 to check a zero-crossing point of the power from the power source 35, generate a zero-crossing point signal and prevent an unnecessary signal from being transmitted to the microcomputer 22.

[0036] The control unit 20 of the dishwasher is configured to alter an amount of current applied to the pump motor 30, depending upon the degree of soil concentration of the wash liquid sensed by the soil degree sensor 25, and thereby regulate the speed of the pump motor 30. Further, the control unit 20 allows the speed of the pump motor 30 to be manually regulated as desired by the operator.

[0037] For example, when the operator desires to wash dishes made of a material that is expensive or that has a low impact resistance, such as crystal, the operator may manipulate the spraying pressure adjustment control 24 to select a desired wash liquid spraying pressure. Thus, the control unit 20 controls the amount of current in response to the spraying pressure adjustment instruction inputted via the spraying pressure adjustment control 24.

[0038] Wash liquid spraying pressures, which are determined depending upon degrees of soil concentrations and rates of concentration change sensed and calculated by the soil degree sensor 25, are provided in TABLE 1. TABLE 1 Rate of Degree of Soil Concentration Wash Liquid Concentration Change Spraying Pressure High High High Intermediate Intermediate Constant Low Intermediate High Intermediate Intermediate Intermediate Constant Low Low Intermediate Intermediate Constant Low

[0039] As can be readily seen from TABLE 1, when the degree of soil concentration is high and the rate of concentration change is high, the control unit 20 determines that the dishes are highly soiled and regulates the speed of the pump motor 30 to high, thus supplying wash liquid at high pressure. Thus, a high pressure of wash liquid is sprayed through the spraying mechanism. When the soil concentration is high and the rate of concentration change is intermediate, the control unit 20 determines that the soiled matter is substantially removed from the dishes, and regulates the speed of the pump motor 30 to intermediate thus supplying wash liquid at intermediate pressure through the spraying mechanism. When the soil concentration is low and a rate of concentration change is constant, the control unit 20 determines that dishes are merely slightly soiled and regulates the speed of the pump motor 30 to low, thus supplying wash liquid at a low pressure the spraying mechanism for a short period of time. In this instance, the amount of wash liquid drawn by the wash pump is decreased, shortening dishwashing time and reducing unnecessary energy consumption.

[0040]FIG. 4 is an exemplary flow chart depicting a method for operating the dishwasher according to as aspect of the present invention.

[0041] At step S1, during a dishwashing operation, the soil degree sensor 25 senses a degree of soil concentration and calculates a rate of concentration change.

[0042] At step S2, the control unit 20 determines, based on TABLE 1, a wash liquid spraying pressure based upon the degree of soil concentration and the rate of concentration change determined by the soil degree sensor 25. Also at step S2, the control unit 20 outputs a control signal to the phase controlling driver circuit 21.

[0043] At step S3, the phase controlling driver circuit 21 regulates the power source, in response to the trigger signal inputted thereto, to supply power to the pump motor 30. As described above with reference to FIGS. 3a, 3 b and 3 c, the power supplied to the pump motor 30 is regulated depending upon a position of the trigger signal.

[0044] At step S4, the speed of the pump motor 30 is determined depending upon the power supplied in the step S3, the pump motor 30 drives the wash pump.

[0045] At step S5, the wash pump pumps wash liquid, thus spraying the wash liquid through the spraying mechanism.

[0046] As apparent from the above description, the dishwasher and the method for operating the same according to the present invention provide advantages. Specifically, since the degree to which the wash liquid is soiled is sensed and a magnitude of current inputted to a pump motor is regulated depending upon the degree to which the wash liquid is soiled, the wash liquid spraying pressure may be adjusted to avoid wasting wash liquid and energy. Moreover, the operator may adjust the wash liquid spraying pressure, as desired, if washing dishes that are expensive or that are made of delicate materials.

[0047] Although the invention has been described with reference to exemplary embodiments, it is understood that the words that have been used are words of description and illustration, rather than words of limitation. Changes may be made within the purview of the appended claims, as presently stated and as amended, without departing from the scope and spirit of the invention in its aspects. Although the invention has been described with reference to particular means, materials and embodiments, the invention is not intended to be limited to the particulars disclosed; rather, the invention extends to all functionally equivalent structures, methods and uses such as are within the scope of the appended claims.

[0048] The present disclosure relates to subject matter contained in priority Korean application No. 2002-05710, filed on Jan. 31, 2002, which is herein expressly incorporated by reference in its entirety. 

What is claimed:
 1. A dishwasher comprising: an interior tub in which dishes to be washed are located; a wash pump for pumping wash liquid for washing the dishes located in the interior tub; a pump motor for driving the wash pump; spraying means for spraying wash liquid onto the dishes; and a control unit for regulating the speed of the pump motor to adjust a spraying pressure of wash liquid sprayed from the spraying means.
 2. The dishwasher as set forth in claim 1, wherein the control unit regulates the speed of the pump motor by controlling a phase of power inputted to the pump motor.
 3. The dishwasher as set forth in claim 1, further comprising a sensor for sensing the degree to which the wash liquid is soiled, upon washing the dishes.
 4. The dishwasher as set forth in claim 3, wherein the sensor senses a soil concentration in the wash liquid and calculates a rate of concentration change of the wash liquid.
 5. The dishwasher as set forth in claim 4, wherein when a sensed soil concentration in the wash liquid is constant and the calculated rate of concentration change is lower than a previous value, the control unit implements a next dishwashing procedure.
 6. The dishwasher as set forth in claim 2, wherein the control unit comprises: a microcomputer for generating and outputting a trigger signal to control the supply of power from a power source to the pump motor; and a phase controlling driver circuit for controlling a phase of power to be supplied from the power source to the pump motor in response to the trigger signal generated and outputted by the microcomputer, wherein the phase controlling driver circuit applies a resulting power to the pump motor.
 7. The dishwasher as set forth in claim 6, wherein the microcomputer controls the phase controlling driver circuit so that a first speed of the pump motor, when a sensed soil concentration is higher than a reference value, is greater than a second speed of the pump motor when a sensed soil concentration is lower than the reference value, wherein a first wash liquid spraying pressure is associated with the first speed and a second wash liquid spraying pressure is associated with the second speed and the first liquid spraying pressure is greater than the second liquid spraying pressure.
 8. The dishwasher as set forth in claim 1, further comprising a spraying pressure adjustment control for allowing an operator to regulate the speed of the pump motor.
 9. A method for operating a dishwasher, comprising: sensing a degree to which wash liquid is soiled, upon washing the dishes; regulating a speed of a pump motor for spraying wash liquid onto dishes in the dishwasher, the regulation depending upon the degree to which wash liquid is soiled as sensed during the sensing; and adjusting a wash liquid spraying pressure depending upon the speed of the pump motor.
 10. The method as set forth in claim 9, further comprising determining the degree of soil concentration in the wash liquid and calculating a rate of concentration change of the wash liquid.
 11. The method as set forth in claim 10, further comprising implementing a next dishwashing procedure when the sensed soil concentration is constant and the calculated rate of concentration change is lower than a previous value.
 12. The method as set forth in claim 9, wherein the speed of the pump motor is regulated such that a first level of power inputted to the pump motor, when a sensed soil concentration is higher than a reference value, is greater than a second level of power inputted to the pump motor when a sensed soil concentration is lower than the reference value.
 13. The method as set forth in claim 9, further comprising receiving an instruction from an operator to adjust the wash liquid spraying pressure, wherein the speed of the pump motor is regulated in response to the instruction for adjusting the wash liquid spraying pressure. 